Automobile floor panel and automobile floor panel manufacturing method

ABSTRACT

A vehicle floor panel is provided in which a honeycomb core made of metal sandwiched and adhered between two CFRP plates is one in which a large number of core units formed into a polygon shape are continuous within one plane so as to share a side of the polygon. Since closed-section parts formed by a hat-shaped cross section part formed along the side and one CFRP plate are continuous with each other at a vertex of the polygon of the adjacent core units, not only is it possible to lighten the weight by opening the interior of the polygon (P) shape core unit, but it is also possible to enhance the energy-absorbing performance by dispersing and transmitting a collision load inputted into one direction of the floor panel toward a plurality of other directions because the high strength load transmission path is continuous with other load transmission paths.

TECHNICAL FIELD

The present invention relates to an automobile floor panel in which ahoneycomb core, made of metal, is sandwiched between two CFRP plates andadhered, and to a manufacturing method for the automobile floor panel.

BACKGROUND ART

A honeycomb panel for use as a wall panel of a structure, etc. that isformed from a honeycomb core having a large number of convex partsformed by subjecting a metal plate such as aluminum to drawing orpress-forming, and a surface material such as a urethane resin or anepoxy resin adhered to opposite faces of the honeycomb core is knownfrom Patent Document 1 below.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent Application Laid-open No. 6-316015

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

This type of honeycomb panel has a large strength toward a load inputtedin a direction orthogonal to the face of the honeycomb core but does nothave sufficient strength toward a load inputted in a direction parallelto the face of the honeycomb core; therefore, when the aboveconventional honeycomb panel is used as an automobile floor panel, if acollision load in a direction parallel to the face of the honeycomb coreis inputted, there is a possibility that it will not be possible toobtain a sufficient energy-absorbing effect.

The present invention has been accomplished in light of the abovecircumstances, and it is an object thereof to provide an automobilefloor panel that can easily be produced and has a high strength toward aload inputted in a direction parallel to the face of a honeycomb core.

Means for Solving the Problems

In order to attain the above object, according to a first aspect of thepresent invention, there is provided an automobile floor panel in whicha honeycomb core made of metal is sandwiched between two CFRP plates andadhered, wherein the honeycomb core is one in which a large number ofcore units formed into a polygon shape are continuous within one planeso as to share a side of the polygon, the side forms a hat-shaped crosssection part having a top face, a pair of side faces and a pair offlange faces, and closed cross-section parts formed by adhering one ofthe CFRP plates to the pair of flange faces and linearly extending alongthe side are continuous with each other at a vertex of the polygon ofthe adjacent core units.

Further, according to a second aspect of the present invention, inaddition to the first aspect, the core unit is a square shape or anequilateral triangle shape.

Furthermore, according to a third aspect of the present invention, inaddition to the first or second aspect, a pair of the honeycomb coresare adhered to each other via the top face of the hat-shaped crosssection part.

Moreover, according to a fourth aspect of the present invention, inaddition to the third aspect, the flange face of the hat-shaped crosssection part of the pair of honeycomb cores is adhered to the CFRP plateby an urethane-based adhesive having a modulus of elasticity of 10 to120 MPa.

Further, according to a fifth aspect of the present invention, inaddition to the third or fourth aspect, the top faces of the hat-shapedcross section parts of the pair of honeycomb cores are adhered to eachother by an epoxy-based adhesive.

Furthermore, according to a sixth aspect of the present invention, inaddition to any one of the first to fifth aspects, end parts of the twoCFRP plates are adhered to each other by an epoxy-based adhesive.

Moreover, according to a seventh aspect of the present invention, inaddition to the third or fourth aspect, the top faces of the hat-shapedcross section parts of the pair of honeycomb cores are adhered to eachother by an urethane-based adhesive having a modulus of elasticity of 10to 120 MPa.

Further, according to an eighth aspect of the present invention, inaddition to any one of the first to seventh aspects, the side faces ofhat-shaped cross section parts that are adjacent to each other arecontinuous while being smoothly curved.

Furthermore, according to a ninth aspect of the present invention, inaddition to any one of the first to eighth aspects, there is provided amanufacturing method for the automobile floor panel, wherein an adhesiveis cured by induction heating the honeycomb core by an IH heater.

Moreover, according to a tenth aspect of the present invention, inaddition to any one of the first to eighth aspects, there is provided amanufacturing method for the automobile floor panel, wherein thehoneycomb core is manufactured by deep drawing an aluminum plate by blowmolding.

Effects of the Invention

In accordance with the first aspect of the present invention, thehoneycomb core made of metal sandwiched and adhered between the two CFRPplates is one in which a large number of core units formed into apolygon shape are continuous within one plane so as to share a side ofthe polygon. Since the side of the polygon forms the hat-shaped crosssection part having a top face, a pair of side faces and a pair offlange faces, and the closed cross-section parts formed by adhering oneCFRP plate to the pair of flange faces and extending linearly along aside are continuous with each other at the vertex of the polygons ofadjacent core units, not only is it possible to lighten the weight byopening the interior of the polygonal core unit, but it is also possibleto enhance the energy-absorbing performance by dispersing andtransmitting a collision load inputted into one direction of the floorpanel toward a plurality of other directions because the high strengthload transmission path formed from the linearly extending closedcross-section part is continuous with a plurality of other loadtransmission paths at the vertex of the polygons of the core units.Moreover, since the honeycomb core made of metal can be press formed, itcan be manufactured inexpensively in a short period of time.

Furthermore, in accordance with the second aspect of the presentinvention, since the core unit is a square or an equilateral triangleshape, it becomes possible to apply an adhesive for adhering the CFRPplate linearly along the top face of the hat-shaped cross section part,thus improving the productivity.

Moreover, in accordance with the third aspect of the present invention,since the pair of honeycomb cores are adhered to each other via the topfaces of the hat-shaped cross section parts, even for a pressedhoneycomb core that has a small thickness due to the difficulty of deepdrawing, a floor panel having a required plate thickness can be obtainedby making it as two layers.

Furthermore, in accordance with the fourth aspect of the presentinvention, since the flange faces of the hat-shaped cross section partsof the pair of honeycomb cores are adhered to the CFRP plate with aurethane-based adhesive having a modulus of elasticity of 10 to 120 MPa,it is possible to suppress vibration of the CFRP plate, which is hardand easily transmits vibration, by a soft urethane-based adhesive.

Moreover, in accordance with the fifth aspect of the present invention,since the top faces of the hat-shaped cross section parts of the pair ofhoneycomb cores are adhered to each other with an epoxy-based adhesive,it is possible to strongly adhere the pair of honeycomb cores with ahigh strength epoxy-based adhesive, and, moreover, since the same typeof materials are adhered to each other, the adhesive strength is furtherimproved.

Furthermore, in accordance with the sixth aspect of the presentinvention, since end parts of the two CFRP plates are adhered to eachother with an epoxy-based adhesive, it is possible to strongly adherethe CFRP plates with a high strength epoxy-based adhesive and, moreover,since the same type of materials are adhered to each other the adhesivestrength is further improved.

Moreover, in accordance with the seventh aspect of the presentinvention, since the top faces of the hat-shaped cross section parts ofthe pair of honeycomb cores are adhered to each other with aurethane-based adhesive having a modulus of elasticity of 10 to 120 MPa,a flexible urethane-based adhesive layer is formed between the pair ofhoneycomb cores, thus suppressing vibration of the floor panel.

Furthermore, in accordance with the eighth aspect of the presentinvention, since the side faces of the hat-shaped cross section partsthat are adjacent to each other are continuous with each other whilebeing smoothly curved, a load that is inputted into the vertex along oneside of the polygon can be efficiently transmitted from the vertex alongthe plurality of sides.

Moreover, in accordance with the ninth aspect of the present invention,since the adhesive is cured by induction heating the honeycomb core byan IH heater, it is possible to shorten the curing time for theadhesive, thus enhancing the production efficiency.

Furthermore, in accordance with the tenth aspect of the presentinvention, since the honeycomb core is manufactured by deep drawing analuminum plate by blow molding, compared with a case in which analuminum plate having the same plate thickness is press formed, deepdrawing becomes possible, and a floor panel having a required platethickness can be obtained without forming the honeycomb core as twolayers, thus reducing the number of components and the production cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a honeycomb panel (sectional view alongline 1-1 in FIG. 2). (first embodiment)

FIG. 2 is a view from arrowed line 2-2 in FIG. 1. (first embodiment)

FIG. 3 is a perspective view of a honeycomb core. (first embodiment)

FIG. 4 is a graph showing the relationship between load and amount ofdeformation of the honeycomb core. (first embodiment)

FIG. 5 is a diagram corresponding to FIG. 2. (second embodiment)

FIG. 6 is a diagram corresponding to FIG. 1. (third embodiment)

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

12 Honeycomb core

13 CFRP plate

14 Core unit

14 a Top face

14 b Side face

14 c Flange face

15 Adhesive

16 Adhesive

17 Adhesive

18 Closed cross-section part

P Polygon

S Side

V Vertex

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are explained by reference to theattached drawings.

First Embodiment

A first embodiment of the present invention is explained below byreference to FIG. 1 to FIG. 4.

As shown in FIG. 1 to FIG. 3, a honeycomb panel 11 used as a floor panelof an automobile is formed from a honeycomb core 12 made of an aluminumalloy and a pair of CFRP plates 13 and 13 adhered to opposite faces ofthe honeycomb core 12. The CFRP plates 13 and 13 are formed by embeddinga carbon fiber as a reinforcing material in the interior of a resin as abase material, and in the present embodiment in a state in which endparts of the pair of CFRP plates 13 and 13 are bent through right anglesoutside the honeycomb core 12, the end parts are superimposed on oneanother and adhered by an adhesive 15.

The honeycomb core 12 is formed by blow molding a material made of analuminum alloy, and a regular hexagonal core unit 14 is repeatedlycontinuous within one plane (see FIG. 2). The basic shape of the coreunit 14 is a polygon (regular hexagon) P comprising six sides S and sixvertexes V; six polygons P are consecutively disposed around one polygonP while sharing six sides S, and three sides S intersect at each vertexV at an angle of 120°. Two core units 14 and 14 sharing one side S ofthe polygon P have a hat-shaped cross section (see FIG. 1) and includeone top face 14 a, two side faces 14 b and 14 b, and two flange faces 14c and 14 c. Since the inner side of the flange face 14 c on the innerperipheral side of the honeycomb core 12 opens in a regular hexagonshape, the weight of the honeycomb core 12 is lightened by a portioncorresponding to the opening.

With regard to the honeycomb core 12, the top face 14 a of thehat-shaped cross section part is adhered to one of the CFRP plates 13with an adhesive 16, and the flange faces 14 c and 14 c of thehat-shaped cross section part are adhered to the other CFRP plate 13with an adhesive 17. As a result, at a position corresponding to theside S of the polygon P with which two core units 14 and 14 are incontact, a trapezoidal closed cross-section part 18 extending linearlyalong the side S is formed from the top face 14 a, the pair of sidefaces 14 b and 14 b, and the other CFRP plate 13, and three of theclosed cross-section parts 18 are combined at the vertex V of thepolygon P with an angle of intersection of 120°.

The side faces 14 b and 14 b of the two sides S, which are combined atthe vertex V of the polygon P, are continuous with each other whilebeing smoothly curved without forming a sharp angle (see FIG. 2).

The operation of the embodiment of the present invention having theabove arrangement is now explained.

When a load from the foot of an occupant is applied to the honeycombpanel 11 used as a floor panel of an automobile in a direction that isorthogonal to the plane, as for a standard honeycomb panel, bytransmitting the load inputted from one of the CFRP plates 13 to thehoneycomb core 12 to the other CFRP plate 13 via the side faces 14 b ofthe hat-shaped cross section part and dispersing it, high strength isexhibited despite of being light weight.

When a collision load in a direction parallel to the plane is applied tothe honeycomb panel 11, the collision load transmitted via a loadtransmission path formed from one high strength linear closedcross-section part 18 of the honeycomb core 12 is dispersed to otherload transmission paths formed from two closed cross-section parts 18and 18 intersecting at the vertex V of the polygon P and transmitted,and this is repeated in sequence to thus disperse the collision load tothe entire honeycomb panel 11, thus preventing localized breakage of thehoneycomb panel 11 and thereby improving the energy-absorbingperformance.

In this process, since the side faces 14 b of the hat-shaped crosssection parts intersecting at the vertex V of the polygon P arecontinuous with each other while being smoothly curved (see FIG. 2), acollision load transmitted via one load transmission path can betransmitted more efficiently to two other load transmission paths anddispersed.

Moreover, the honeycomb core 12 has isotropy since it is formed bycontinuously assembling a large number of regular hexagonal core units14, and it can exhibit unchanged energy-absorbing performance regardlessof whether the collision load is that of a frontal collision or thecollision load is that of a side collision.

Furthermore, since the honeycomb core 12 is made of an aluminum alloy,which is more ductile than one made of CFRP, as shown in FIG. 4, whenthe input load increases, it does not break suddenly but undergoesconsecutive plastic deformation and exhibits a high energy-absorbingperformance. Moreover, due to the honeycomb core 12 being blow molded,compared with press forming, deep drawing becomes possible, a sufficientthickness can be given to the honeycomb panel 11 with only one layer ofhoneycomb core 12, and the cost can be reduced due to the number ofcomponents being cut. Furthermore, since the honeycomb core 12 is madeof an aluminum alloy, not only is it inexpensive compared with one madeof CFRP, but it is also possible to carry out induction heating using anIH heater, thus enabling the curing time to be shortened by heating theadhesives 15, 16, and 17 with an IH heater during production and,furthermore, enabling swaging by utilizing the ductility of an aluminumalloy or welding to be carried out.

Second Embodiment

A second embodiment of the present invention is now explained byreference to FIG. 5.

In the first embodiment the core unit 14 is a regular hexagon, but thesecond embodiment is different in that the core unit 14 is a square. Inaccordance with the present embodiment, in addition to the operationaleffects of the first embodiment, since the top faces 14 a and the flangefaces 14 c of the plurality of hat-shaped cross section parts, which arecontinuous, are aligned linearly, when a coating operation of theadhesive 16 or 17 is carried out using a robot, it is possible to move arobot arm linearly without moving it in a zig-zag manner, thus enablinga further operational effect of improving the operating efficiency to beachieved.

Third Embodiment

A third embodiment of the present invention is now explained byreference to FIG. 6.

The third embodiment is one in which, with regard to the honeycomb panel11 of the first embodiment, two honeycomb cores 12 and 12 formed bypress forming and not by blow molding are stacked into two layers andadhered by the adhesive 16 via the top faces 14 a of the hat-shapedcross section parts. In this process, as the adhesive 17 for adheringthe flange faces 14 c of the hat-shaped cross section part of thehoneycomb core 12 to the CFRP plates 13 and 13, a urethane-based elasticadhesive having a modulus of elasticity of 10 to 120 MPa is used.Furthermore, an epoxy-based adhesive is used as the adhesive 16 foradhering the top faces 14 a of the hat-shaped cross section parts of thetwo honeycomb cores 12 and 12 to each other and as the adhesive 15 foradhering end parts of the CFRP plates 13 and 13 to each other.

In accordance with the present embodiment, since due to the honeycombcores 12 being stacked as two layers, each layer of the honeycomb cores12 can be made thinner compared with the first embodiment, it becomespossible to manufacture the honeycomb core 12 by press forming, forwhich deep drawing is difficult, and the manufacturing cost can be cutfurther. Furthermore, the CFRP plates 13 and 13, which are hard, havethe problem that due to their modulus of elasticity being 230 to 650 MPavibration can be transmitted easily, but since the flange faces 14 c ofthe hat-shaped cross section parts of the honeycomb core 12 and the CFRPplates 13 and 13 are adhered by the urethane-based adhesive 17 having alow modulus of elasticity, vibration and noise of the honeycomb panel 11can be reduced. Moreover, since the epoxy-based adhesive 16 for adheringthe top faces 14 a of the hat-shaped cross section parts to each otherand the epoxy-based adhesive 15 for adhering end parts of the CFRPplates 13 and 13 to each other have a high adhesive strength comparedwith a urethane-based adhesive, the strength of the adhered parts can beincreased and, furthermore, since the same type of members are adheredto each other the adhesive strength can be improved further.

Embodiments of the present invention are explained above, but thepresent invention may be modified in a variety of ways as long as themodifications do not depart from the spirit and scope thereof.

For example, the shape of the polygon P of the core unit 14 is notlimited to a regular hexagon or a square and may be an equilateraltriangle.

Furthermore, in the third embodiment, the top faces 14 a of thehat-shaped cross section parts of the two honeycomb cores 12 and 12 areadhered to each other with the epoxy-based adhesive 16, but they may beadhered with a urethane-based elastic adhesive having a modulus ofelasticity of 10 to 120 MPa. In accordance with this, it is possible toreduce the vibration and noise of the honeycomb panel 11 by theurethane-based adhesive 17 having a low modulus of elasticity.

1. A vehicle floor panel in which a honeycomb core (12) made of metal issandwiched between two CFRP plates (13) and adhered, wherein thehoneycomb core (12) is one in which a large number of core units (14)formed into a polygon (P) shape are continuous within one plane so as toshare a side (S) of the polygon (P), the side (S) forms a hat-shapedcross section part having a top face (14 a), a pair of side faces (14 b)and a pair of flange faces (14 c), and closed cross-section parts (18)formed by adhering one of the CFRP plates (13) to the pair of flangefaces (14 c) and linearly extending along the side (S) are continuouswith each other at a vertex (V) of the polygon (P) of the adjacent coreunits (14).
 2. The vehicle floor panel according to claim 1, wherein thecore unit (14) is a square shape or an equilateral triangle shape. 3.The vehicle floor panel according to claim 1, wherein a pair of thehoneycomb cores (12) are adhered to each other via the top face (14 a)of the hat-shaped cross section part.
 4. The vehicle floor panelaccording to claim 3, wherein the flange face (14 c) of the hat-shapedcross section part of the pair of honeycomb cores (12) is adhered to theCFRP plate (13) by an urethane-based adhesive (17) having a modulus ofelasticity of 10 to 120 MPa.
 5. The vehicle floor panel according toclaim 3, wherein the top faces (14 a) of the hat-shaped cross sectionparts of the pair of honeycomb cores (12) are adhered to each other byan epoxy-based adhesive (16).
 6. The vehicle floor panel according toclaim 1, wherein end parts of the two CFRP plates (13) are adhered toeach other by an epoxy-based adhesive (15).
 7. The vehicle floor panelaccording to claim 3, wherein the top faces (14 a) of the hat-shapedcross section parts of the pair of honeycomb cores (12) are adhered toeach other by an urethane-based adhesive (16) having a modulus ofelasticity of 10 to 120 MPa.
 8. The vehicle floor panel according toclaim 1, wherein the side faces (14 b) of hat-shaped cross section partsthat are adjacent to each other are continuous while being smoothlycurved.
 9. A manufacturing method for the vehicle floor panel accordingto claim 1, wherein an adhesive is cured by induction heating thehoneycomb core (12) by an IH heater.
 10. A manufacturing method for thevehicle floor panel according to claim 1, wherein the honeycomb core(12) is manufactured by deep drawing an aluminum plate by blow molding.